This invention relates to chemical mechanical polishing machines for planarizing semi-conductor wafers; and in particular to such machines having improved bearings.
Chemical mechanical polishing machines for semiconductor wafers are well known in the art, as described for example in U.S. Pat. Nos. 5,335,453, 5,329,732, 5,287,663, 5,297,361 and 4,811,522. Typically, such polishing machines utilize mechanical bearings for the polishing pad and the wafer holder. Such mechanical bearings can provide disadvantages in operation. Mechanical bearings can become contaminated with the abrasive slurry used in the polishing process. If mechanical bearings provide point or line support for a polishing pad platen, the possibility of cantilever bending of the platen arises. Bearing vibrations can result in undesirable noise, and bearing adjustment typically requires a mechanical adjustment of the assembly. This adjustment is typically a high-precision, time-consuming adjustment.
It is an object of the present invention to provide a chemical mechanical polishing machine having fluid bearings that to a large extent overcome the problems set out above, and that can easily be adjusted to control polishing forces.